Mass spectrometry analyses for determining whether 13C615N2-labeled lysines contained in the elafin (innate peptide highly expressed in lower female genital tract and down-regulated in case of HPV infection) were found in the amino acid sequence of some proteins of Lactobacilli, supporting the fundamental role of innate secretion in the growth/survival of acid lactic bacteria (L. crispatus, L. jensenii and L. iners).